Search

Copyright of Canadian Journal of Microbiology is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Four experiments were conducted to assess the effect of foliar applications of various nutrient solutions on the phylloplane yeast community of tall fescue ( Festuca arundinacea Schreb.). In the first three experiments, increasing concentrations of sucrose (2–16%), yeast extract (0.5–2.5%), and sucrose plus yeast extract (2.5–18.5% total) were applied and the yeast colony forming units (cfu) enumerated 14 h later by dilution plating. Significant positive linear relationships were observed between the number of yeast cfu and applications of both yeast extract and sucrose plus yeast extract. Foliar applications of sucrose alone had no significant effect on yeast community abundance, indicating that phylloplane yeasts of turfgrass are not limited by the amount or availability of carbohydrates. In the fourth experiment, five different solutions were applied to tall fescue to investigate the response of the yeast community to organic and inorganic nitrogen sources. Tryptone or yeast extract, both with considerable amino acid composition, significantly increased the yeast population, while yeast nitrogen base (with or without amino acids) and ammonium sulfate had no affect on yeast abundance. These results suggest that organic nitrogen stimulate yeast community growth and development on the phylloplane of tall fescue, while carbohydrates, inorganic nitrogen, and non-nitrogenous nutrients have little positive effect. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Microbiology is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Microbiology is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Application of yeasts as biocontrol agents to prevent mold decay of fruits and vegetables has been described. We examined 10 yeasts for potential antagonistic activity against survival and growth of Salmonella Poona in cantaloupe juice and decay by Cladosporium cladosporioides and Geotrichum candidum in wounds on cantaloupe rind. Cantaloupe juice was inoculated using five schemes: Salmonella Poona only (1.10 log CFU/ml), high (3.93 to 5.21 log CFU/ml) or low populations (1.79 to 3.26 log CFU/ml) of yeasts only, and Salmonella Poona combined with high or low populations of yeasts. High initial populations of Debaryomyces hansenii Pichia guilliermondii, and Pseudozyma sp. were antagonistic to Salmonella Poona in cantaloupe juice stored at 20°C for 48 h. Wounds in cantaloupe rinds were inoculated with yeast and mold or yeast, mold, and Salmonella Poona, and cantaloupes were stored at 4°C for 14 days or 20°C for 7 days. The pH of rind tissue inoculated with C. cladosporioides and yeasts increased significantly (P ⩽ 0.05) at 20°C. Wounds that were inoculated with P. guilliermondii, together with C. cladosporioides or G. candidum, did not show mold growth at 4 and 20°C. Populations of Salmonella Poona (6.40, 7.26, and 7.98 log CFU per sample) were lower in wounds coinoculated with G. candidum and three of the test yeasts (D. hansenii, P. guilliermondii, and Cryptococcus albidus, respectively) compared to coinoculation with G. candidum or the other seven yeasts. Candida oleophila and Rhodotorula glutinis showed the most promise in reducing the population of Salmonella Poona in wounds in rinds of cantaloupes coinoculated with G. candidum and stored at 4°C. [ABSTRACT FROM AUTHOR]

The influence of inoculum and nutrient concentrations on the in vitro antagonism of Botrytis cinerea by phylloplane yeasts was investigated with detached leaf disk and conidial germination assays. Rhodosporidium toruloides Y-1091 significantly reduced lesion development after 96 h on geranium leaf disks when co-inoculated at 1 × 10[sup 6] or 1 × 10[sup 7] yeast cells/mL with B. cinerea conidia at 1 × 10[sup 4] or 1 × 10[sup 5] conidia/mL. No effect on lesion development was observed when yeast and fungus were co-inoculated at a 1:1 ratio. Biocontrol activity of R. toruloides was greatest in 20 mM glucose and 20-fold dilute yeast nitrogen base. Twenty-five phylloplane yeasts exhibited a wide range of biocontrol activity when screened for antagonism of B. cinerea on geranium leaf disks (1 × 10[sup 6] yeast cells/mL, 1 × 10[sup 5] conidia/mL). Lesion development was significantly reduced by yeasts initially identified as poor antagonists when inoculated at higher concentrations (5 × 10[sup 6] or 1 × 10[sup 7] yeast cells/mL) with B. cinerea. Both poor and good antagonists significantly reduced in vitro germination of B. cinerea conidia. The presence of B. cinerea conidia had a greater effect on the growth of two poor antagonists compared with two good antagonists on leaf disks. These data suggest that many phylloplane yeasts will antagonize B. cinerea under conditions of low nutrient availability and with high antagonist to pathogen ratios.Key words: yeast, biological control, competition, nutrients, germination, Rhodosporidium toruloides.L'auteur à étudié, in vitro, l'influence des concentrations d'inoculum et de nutriments sur l'antagonisme des levures du phylloplan envers le Botrytis cinerea, en utilisant des disques de feuilles détachées et la germination des conidies. Le Rhodosporidium toruloides Y-1091 réduit significativement le développement des lésions après 96 h sur des disques foliaires de géranium, lorsqu'inoculé à raison de 1 × 10[sup 6] ou 1 × 10[sup 7] cellules de levure par millilitre, et 1 × 10[sup 4] ou 1 × 10[sup 5] conidies du B. cinerea par millilitre. On observe aucun effet sur le développement des lésions lorsque la levure et le champignon sont co-inoculés dans un ratio 1:1. L'activité de maîtrise du R. toruloides est plus élevée avec du glucose 20 mM et une base azotée de levure diluée 20 fois. Vingt-cinq levures du phylloplan ont montré une large gamme d'activités de maîtrise biologique, suite à l'évaluation de leur antagonisme envers le B.cinerea, sur disques de feuilles de géranium (1 × 10[sup 6] cellules de levure par millilitre, 1 × 10[sup 5 ] conidies par millilitre). Le développement des lésions est significativement réduit par des levures préalablement identifiées comme faibles antagonistes, pourvu qu'on les inocule à fortes concentrations (5 × 10[sup 6] ou 1 × 10[sup 7] cellules de levure par millilitre) avec le B. cinerea. Les faibles aussi bien que les bons antagonistes réduisent significativement la germination in vitro des conidies du B. cinerea. La présence des conidies du B. cinerea exerce un effet plus marqué sur la croissance de deux antagonistes faibles, comparativement à deux bons antagonistes, sur disques foliaires. Ces données suggèrent que plusieurs levures du phylloplan sont capables de contrer le B. cinerea sous des conditions de faible disponibilité en nutriments et avec de forts ratios antagoniste versus pathogène.Mots clés : levure, lutte biologique, compétition, nutriments, germination, Rhodosporidium toruloides.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

The effects of fungicides on population size and the development of fungicide resistance in the phylloplane yeast flora of bentgrass was investigated. In the spring of 2001, azoxystrobin, chlorothalonil, flutolanil, and propiconazole were applied separately over a 6-week period to creeping bentgrass (Agrostis palustris Huds.). Total and fungicide-resistant yeast populations were assessed by dilution plating onto either potato dextrose agar or potato dextrose agar amended with the test fungicides. Total yeast populations in the fungicide- treated plots were significantly lower than the check plots on three out of four sample dates. In the fall, azoxystrobin or propiconazole were applied twice to the bentgrass over 3 weeks. Significantly larger total yeast populations were observed compared with resistant or highly resistant populations for each treatment on every sample date. Total yeast populations were significantly higher in the check plots compared with either the propiconazole- or azoxystrobin-treated plots on the first three of five sample dates. A collection of yeasts (N = 114) with no prior exposure to fungicides were more sensitive to chlorothalonil, propiconazole, flutolanil, and iprodione than a second group (N = 115) isolated from fungicide-treated turfgrass. These results suggest that fungicide resistance among phylloplane yeasts is widespread and could be an important factor in the development of biological control agents for turfgrass diseases.Key words: yeast, biological control, fungicide, resistance, phylloplane.Nous avons évalué l'effet de fongicides sur la taille de la population et le développement de la résistance aux fongicides chez les levures de la flore du phylloplan de l'agrostis. Au printemps 2001, de l'azoxystrobine, du chlorothalonil, du flutolanil et du propiconazole ont été appliqués séparément pendant une période de 6 semaines sur de l'agrostis blanc (Agrostis palustris Huds.). Les populations de levures totales ou résistantes aux fongicides ont été dénombrées par étalement de dilutions sur gélose dextrose-pomme de terre ou gélose dextrose-pomme de terre additionnée des fongicides vérifiés. Dans les lots traités avec un fongicide les populations de levures totales étaient significativement plus faibles que dans les lots de contrôle pour trois des quatre dates d'échantillonnage. A l'automne, de l'azoxystrobine ou du propiconazole ont été appliqués chez l'agrostis sur une période de 3 semaines. Nous avons observé des populations de levures totales significativement plus élevées que les populations résistantes ou fortement résistantes pour chacun des fongicides et chacune des dates d'échantillonnage. La population de levures était significativement plus élevée dans les lots témoins que dans les lots traités avec l'un ou l'autre de ces fongicides lors des trois premières des cinq dates d'échantillonnage. Une collection de levures (N = 114) sans exposition préalable aux fongicides s'est révélée plus sensible au chlorothalonil, au propiconazole, au flutolanil et à l'iprodione qu'un second groupe (N = 115) isolé de gazons traités avec des fongicides. Ces résultats suggèrent que la résistance aux fongicides chez les levures du phylloplan est très répandue et qu'elle pourrait être un facteur important dans le développement d'agents de contrôle biologique contre les maladies du gazon.Mots clés : levures, contrôle biologique, fongicide, résistance, phylloplan.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

Investigates the adhesion mechanisms of leaf surface yeasts and presents the basidiomycetous yeast Rhodosporidium toruloides (R. toruloides) Banno as a model system. Characterization of cell surface polysaccharides; Effect of lectins on adhesion of R. toruloides; Dual attachment phenotype and differential India ink staining patterns of R. toruloides.